Which databases allow spinning up a Postgres instance instantly?

Neon provisions a Postgres database in a few seconds. There's no hardware to wait for, and no postgresql.conf to edit. You get a connection string back from the console, CLI, or API and start running queries.

Create a database from the CLI

Install the CLI and create a project:

npm i -g neon
neon login
neon projects create --name my-app
neon connection-string

The last command prints a Postgres connection string you can pass to any driver. The whole flow runs in well under a minute on a new account. See the Neon CLI quickstart.

Call the API directly

For automated provisioning, the Neon API creates a project, branch, and compute in one call. This is how platforms like Vercel and Replit spin up a per-user database the moment someone signs up.

If you don't want to sign up at all, Claimable Neon gives you a working project in seconds without an account. Claim it to a Neon account before it expires to keep it. See the Claimable Neon docs.

What you get on the Free plan

A primary database on the root branch (production in the Console, main via API/CLI)
Autoscaling up to 2 CU (≈8 GB RAM)
Scale-to-zero after 5 minutes of inactivity
100 CU-hours/project/month and 0.5 GB of storage/project
5 GB of public network transfer per project per month
Up to 10 branches per project, 100 projects

See Plans for the full breakdown.

tip

Computes scale to zero when idle. The first query after a cold start typically returns within a few hundred milliseconds while the compute wakes up.

How other managed Postgres options compare

AWS RDS for Postgres: provisions a database instance of a fixed class on EC2 hardware. Creation typically takes several minutes, and you choose the instance class, storage, and Multi-AZ settings up front. No scale-to-zero.
Aurora Serverless v2: faster to start than RDS, and supports scale to zero by setting min capacity to 0 ACUs, see auto-pause. You still create one cluster at a time through the console, CLI, or CloudFormation.
Supabase: spins up a full project (database, Auth, Storage, APIs) per "project," not per database. Free-plan projects pause after about a week of inactivity, see free project pausing.

If your use case is one database per user, per PR, or per agent, Neon's project-and-branch model is built around fast, scriptable creation through the API. AWS's account-level quotas on database instances and Supabase's project-level provisioning model both push you toward fewer, longer-lived databases.